1. Field of the Invention
The present invention relates to a thermosetting aqueous-type emulsion of nadimide prepared by dispersing an alkenyl-substituted nadimide in water. It can be used without an organic solvent or with a reduced amount of an organic solvent and is suitable for use as a paint, a coating material or an adhesive.
2. Description of the Prior Art
Conventionally, various resins have been used together with organic solvents in order to improve working performances by enhancing fluidity. However, because of the recent worldwide concern over the influence of organic solvents to pollution of the aerospace and underground environments, e.g. groundwater, non-use or reduced-use of organic solvents is actively promoted in the field of paints, coating materials and adhesives. The use of organic solvents is not desirable because it accompanies evaporation of large amounts of organic solvents in the air.
To make an aqueous-type emulsion of resin materials is a typical countermeasure for the non-use of organic solvents, and various aqueous-type resin emulsions are known in the art. With regard to imide resins which have excellent heat resistance, however, only known aqueous-type emulsions are those of maleimide compounds (for example, U.S. Pat. No. 5,023,339).
There are two types of maleimide compounds, one having two maleimide groups (e.g. bismaleimide) and the other having only one maleimide group (e.g. phenylmaleimide). The former is known to easily produce polyimide having excellent heat resistance only by heating. Whereas until now, it is not yet known that the latter can produce polyimide having excellent heat resistance only by heating.
The above-mentioned emulsion disclosed in U.S. Pat. No. 5,023,339 is the emulsion made from a compound having only one maleimide group, not a compound having two maleimide groups which is convertible into highly heat resistant polyimide. This emulsion, therefore, has no good applicability as a paint, a coating material, or an adhesive. That is, until now there is no aqueous-type emulsion of an imide compound which is convertible into a cured material only by removing water from the emulsion and by heating. If such an aqueous-type emulsion of imide can be prepared, it is usable as a paint, a coating material, or an adhesive. Development of such an aqueous-type emulsion has therefore been desired.